1. Field of the Invention
The present invention relates to a cemented lens and an optical system having the same, which are suitably used for the optical system of, for example, a silver halide film camera, digital still camera, video camera, digital video camera, telescope, binoculars, projector, or copying machine.
2. Description of the Related Art
Optical systems used for recent optical apparatuses such as digital cameras and video cameras are required to have high performance and be compact and lightweight as a whole. In general, as an optical system is miniaturized, chromatic aberration typified in particular by axial chromatic aberration and chromatic aberration of magnification tends to occur more frequently, and the optical performance tends to deteriorate.
It is difficult for an optical system using only an existing optical material such as glass to satisfy both the requirement for high performance and the requirement for miniaturization and weight reduction. As a means for solving such a problem, there is known a method of performing achromatization (chromatic aberration correction) by using an anomalous dispersion material as a material for some lenses of an optical system.
Recently, as a solid material (optical material) having an anomalous dispersion characteristic, a mixture obtained by dispersing Indium-Tin Oxide (ITO) fine particles or TiO2 fine particles in a transparent medium or a combination of solid materials made of resins has been proposed. An optical system having undergone achromatization using lenses made of these materials is known (Japanese Patent Laid-Open No. 2007-163964).
Using a plurality of optical elements made of solid materials having anomalous dispersion characteristics in an optical system makes it easy to correct the chromatic aberration of the overall optical system and to obtain high optical performance while miniaturizing the overall optical system.
Conventionally, when a plurality of optical elements made of solid materials having anomalous dispersion characteristics, they are independently used at a plurality of positions in an optical system without being cemented.
In this arrangement, it is difficult to continuously manufacture optical elements made of solid materials having anomalous dispersion characteristics in a series of steps.
That is, it is necessary to use a plurality of means for manufacturing these elements, and hence a manufacturing process and a manufacturing apparatus become complicated.
In addition, if a plurality of optical elements made of solid materials having anomalous dispersion characteristics are separately arranged at different positions in an optical system, environmental fluctuations have different effects on the respective optical elements.
As a consequence, the optical performance of the respective optical elements changes differently. This greatly changes the optical performance as a whole. As described above, when a plurality of optical elements made of solid materials having anomalous dispersion characteristics are separately arranged, the environmental resistance may deteriorate.
Arranging a plurality of optical elements made of solid materials having anomalous dispersion characteristics facilitates chromatic aberration correction as compared with the case in which one such element is used. Even if, however, a plurality of optical elements made of solid materials having anomalous dispersion characteristics are simply arranged in an optical system, it is difficult to properly correct chromatic aberration and obtain high optical performance unless anomalous dispersion characteristic values, refracting power, and the like are properly set.